Hormone Therapy Adds to Brain Shrinkage

Previous studies showed that hormone therapy in the form of conjugated equine estrogens (CEEs), with or without added progestin, increased the likelihood that older women would have difficulty with thinking skills and memory and experience dementia or cognitive impairment. Because these drugs are known to increase women’s risk for strokes, it had been assumed that these drugs adversely affected women’s memory by increasing the rates of “silent strokes” and brain lesions, changes in tissue that occur when blood flow to an area of the brain is reduced or blocked.

Instead, investigators found that the volumes of brain lesions were not significantly increased among women prescribed hormone therapy, but that the total volumes of brain tissue in regions critical to memory were slightly smaller.

In the first study, a research team led by Laura H. Coker did not find support for the hypothesis that hormone therapy was linked to increases in small vascular lesions in the brain or silent strokes. “We designed,” Coker said, “a study to obtain MRI scans of women’s brains to look for increased volumes of brain lesions among those participants who had taken hormone therapy, compared to those who had not.” More than 1,400 women, ages 71 to 89, who had previously participated in hormone therapy studies for an average of four to six years, participated. “This is not what we expected to find,” Coker said.

In the companion paper, researchers report that the women who had taken hormone therapy had slightly smaller brain volumes in two critical areas of the brain: the frontal lobe and the hippocampus. Both areas are involved in thinking and memory skills, and loss of volume in the hippocampus is a risk factor for dementia.

“Our findings suggest that hormone therapy in older post-menopausal women has a negative effect on brain structures important in maintaining normal memory functioning. However, this negative effect was most pronounced in women who already may have had some memory problems before using hormone therapy, suggesting that the therapy may have accelerated a neurodegenerative disease process that had already begun”, said Susan Resnick, lead author for the second paper.